To ensure your makeup is safe to wear, follow all directions on the label, close containers tightly when not in use, wash your hands before applying makeup and avoid storing cosmetics in places that are above 85 degrees Fahrenheit (29 degrees Celsius) [source: FDA].
To determine if you truly have an allergy to your makeup, you may need to visit a dermatologist. He or she will likely conduct an allergy patch test, in which some of the substance you believe you are allergic to is applied to your skin, then taped over. The doctor then looks at it after 24 hours and again after 48 hours to see the extent of the reaction [source: Henochowicz].
If you find that you have an allergy to an ingredient commonly used in makeup, buying products without that item is the best way to avoid another allergic reaction. Buying cosmetics that are simply marked "hypoallergenic" may not be the ideal solution. In fact, the U.S. Food and Drug Administration does not mandate what standards a product labeled hypoallergenic must meet, so manufacturers have lots of leeway in using the term. Instead, if you know what ingredient causes problems for your skin, make sure you read the label -- which is required by the FDA to list all ingredients -- and ensure that the product you intend to buy is free of the problem substance [source: Stöppler].
To treat a case of mild skin irritation caused by a reaction to makeup, stop using the product you believe may be causing it, apply an anti-itch cream and avoid scratching the area. If you aren't sure which cosmetic is causing the problem, first eliminate those with added dyes and fragrances, which can be more likely to cause a reaction [source: Mayo Clinic].